my firends car had the center berring and trans mounts go out and i kno how that feels. it goes completely away at 10 to 15 mph its like that initial accalaration. i think its heat related because in the morning when i go to school. i leave my street and am yet to feel it or hear it then but after that during the day it happens. that leads me to bieleve possibly no fluid in the diff but i don't know